"Not worth a straw" nghĩa là gì?

Ví dụ 

His opinion is not worth a straw to me.

The current weather forecast is a bit like that: Scorching heat (nóng như thiêu đốt) on Friday , significant (đáng kể) risk of rain on Saturday (22-25°C – that setup which sort of worked on Friday? It’s not worth a straw now …). Sunday could be either or a mixture of both. Still too early to tell.

The worst possibility (khả năng xấu nhất) would be that the jet's (máy bay phản lực) pilot had a mission to provoke (kích động) Syria's air-defense (lực lượng phòng không) to fire, or at best, the lives of innocent (vô tội) women and children in this flight didn't worth a straw for this U.S's air force pilot whose mindset seemed much like an Indian-killer cowboy with his rifle (súng trường).  

Bài trước :"Take a straw poll" nghĩa là gì?